Magnetically encoded data can be readily copied and transferred from one magnetic storage media, such as magnetic striped plastic cards, to another magnetic media or plastic, such as magnetic striped paper cards or magnetic tape. The role of the magnetic striped paper and plastic card has grown rapidly since the first bankcard credit program was launched in 1946. This rapid growth has been accompanied by an even greater opportunity for fraud and counterfeiting. Altering, copying, and counterfeiting are longstanding and well known growing problems in the payment systems industry.
Magnetic stripe technology is utilized by the payment systems industry in the United States and on a worldwide basis. The physical characteristics of the magnetic stripe are explicitly specified, encoding standards are well defined, and the specifications are contained in publicly available standards such as ISO standard 7811/2-1985(E) which describes the encoding associated with such cards. Magnetized regions in the strip, representing digital data, are encoded using these established standards to represent binary digits 0 and 1. Encoding electronics set-up the specification to place the data in a timing sequence that appears as a spatial sequence on the magnetic stripe. Decode electronics require a minimum readback signal amplitude to detect the flux reversal position and the timing between flux reversals provide for the data to be decoded. Magnetic strip technology has been utilized in many applications where security and reliability have been compromised by the ease by which the data can be re-encoded and read.
Historically, various techniques and attempts have been made to authenticate the magnetically encoded data and protect such documents from counterfeiting. One known technology is disclosed in U.S. Pat. No. 4,023,204 issued to Lee for Watermark Magnetics. The Watermark Magnetics technology relies on a predetermined structuring of the magnetic particles as the magnetic tape is being made. A predetermined structure is oriented and solidified into the magnetic particle alignment when the slurry of magnetic material is dried onto the tape backing during the manufacturing process. This is similar to placing aligned sticks into a concrete mix in which the sticks remain in that alignment when the concrete slurry has dried. The detection and decoding of this pattern requires special magnetic read heads and decode circuits which are sensitive to the alignment of the magnetic particles. This method has proven to be reliable but expensive and resulted in increased manufacturing costs.
Another type of document security system is disclosed in U.S. Pat. No. 4,423,415 issued to Goldman which uses light absorption by paper to derive a unique characteristic for the specific document. The unique characteristic is derived from physical inherent properties of the random position and the light absorption of the paper fibers within the document itself. It is related to absorption of a light beam to read and reproduce the characteristic which is an analog wave shape of the light absorption pattern or a digitized number that represents the analog characteristic. This can be used to recreate the analog wave shape characteristic and compared to the subsequent verification of the original document. The technology disclosed by Goldman relates to visible light and the variable absorption of light by random paper fibers.
A variation in the above described optically based system to authenticate magnetically based information is described in U.S. Pat. No. 4,650,978 issued to Hudson and Fernandez. The system described by the Hudson patent uses the intrinsic properties of the magnetic stripe to shift the amplitude of the wave form of an analog recording. The method utilizes a shift in the amplitude of a non-saturated analog recording which can not be applied to a shift in the timing sequence of digital saturation encoding. The use of analog patterns is complex, hard to analyze, and requires the use of expensive circuitry.
U.S. Pat. No. 4,837,426 issued to Pease et al. also uses intrinsic variations of the magnetic media to produce variations in the signal amplitude for both digital and analog signals. This patent depends on detecting a continuous, unique, permanent and randomly varying characteristic of the recordable region of magnetic material being sensed which is the signal amplitude and does not include any component from the random and inherent variations in the timing of magnetically encoded data. The Pease patent discloses a method and an amplifier apparatus to enhance the detectability of the sensed random magnetic media characteristic by recording an electrical signal to produce variations in the signal amplitude. Practicing the method of this patent requires sensing the amplitude signal of permanent and randomly varying magnetic characteristics of magnetic media through shifts in the amplitude of the digital encoding which is then used to form a unique representation. This representation is subsequently encoded onto a separate track of the magnetic material or stored in a central data base for latter comparisons. This technique utilizes amplitude ratios not random timing variations in the encoded data to develop the unique representation; so copying and counterfeiting can be accomplished through such techniques as high frequency bias recording and electronic copy circuits.
Each of the known systems appear to be somewhat effective in authenticating magnetically encoded information but each such system heretofore has limitations. Optical based verification systems require reflective light or translucent media. Reflective light systems can not be used to verify many types of objects. Structured magnetic tapes require expensive special magnetic tape and special reading equipment. Use of amplitude ratios, distinct magnetic layers, and analog patterns are complex, hard to interface with existing systems; and in some cases, the security feature can be compromised by the use of high frequency bias recording, accurate copying device, or other relatively simple methods.
An object of this invention is to use the inherent properties of standard magnetic storage media to secure the data by utilizing the inherent variations in the timing of magnetically encoded data. This results in not requiring special read heads to read security codes in separate tracks. A further object of this invention is to achieve the improved security benefits with high coercivity tape, Watermark Magnetic tape, and other special magnetic media materials.
Another object of this invention is to use simple cost effective digital techniques to secure the data from alteration, counterfeiting, skimming, and buffering. The present invention utilizes the variations in flux timing locations or jitter to develop a unique and repeatable identification characteristic for encoding magnetic stripes which is identified herein as the Jitter Signature.
A further object of this invention is to utilize the innate jitter pattern of other magnetic technologies, such as Watermark Magnetics to develop and encode a Jitter Signature number for that Watermark Magnetics jitter pattern. The Watermark Magnetics Jitter Signature number is encoded in a standard track to bond the user's data to the permanent Watermark Magnetics pattern that can not be copied to another card.
Another object is to use the innate pattern contained in Watermark Magnetics to further enhance the Jitter Signature of the F2F encoding.
An object of this invention is to purposefully modify the bit period jitter present in encoded magnetic media by a quantity greater than the random intrinsic bit to relative jitter. This jitter modification or modulation is achieved by modifying the standardized Akien Double Frequency F2F encoding bit periods and not the F2F bit value itself. These jitter enhancing techniques may be applied to structured magnetic technologies such as Watermark Magnetics or high coercivity tapes.
This invention possesses other objects and features of advantage which will become apparent from the following description taken in conjunction with the accompanying drawings.